Thermometer



(Modem V r W. ALWALES. Thermometer;

No. 240,058. Patented April 12,1881.

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NJ'EIERS. PHOTO-LITNDGRAFHER, WASHINGTON. D,-C.

UNITED STATES PATENT OFF CE.

WILLIAM A. WALES, OF NEWTON, ASSIGNOR TO THE AUBURNDALE lVATOl-I COMPANY, OF WESTON, MASSACHUSETTS.

THERMOMETER.

SPECIFICATION formingpart of Letters Patent No. 240,058, dated April 12, 1881.

Application filed November 6, 1880. (Model.)

1 To all whom it may concern:

Be it known that I, WILLIAM A. WALES, a citizen of the United States, residing at Newton, in the county of Middlesex, and in the State of Massachusetts, have invented a new and useful Thermometer, of which the following is a specification.

This invention relates to certain improvements in that class of instruments known as mechanical thermometers, in which the changes of temperature are noted by means of a dial and pointer or index operated by the unequal expansion of strips of different metal.

This class of instruments are noted for their extreme delicacy and sensitiveness to the smallest changes in temperature, and the time required for registering a difference of many degrees is only a few seconds. This extreme susceptibility of the bimetallic strip, which operates the registering device, tends to produce a tremulous, unsteady, and unequal movement of the index-hand, the fluctuations caused by the varied expansion or contraction of such strip being multiplied by the long leverage through which the motion is transmitted.

In devices of this class hitherto in use various methods have been employed to counteract this evil, such as the use of a hair-spring upon the pointer-shaft. None of these devices, so far as I am aware, have completely succeeded in accomplishing their purpose.

The object of my invention is to provide a regulating and governing device for causing a uniform movement of the index-hand, or for holding it when at rest perfectly stationary without fluctuation. These objects I attain by the apparatus and mechanism illustrated in the accompanying drawings, in which Figure 1 represents a view, in perspective, of the device complete; and Fig. 2, a view showing the mechanism detached.

The letter A indicates a casing, which may be constructed of metal, hard rubber, or other suitable material. The said case is preferably made cylindrical in shape, and is constructed in two parts, similar to a pocket-compass case, the said parts being separable, so as to place the works Within convenient reach for cleaning or repair. The interior of the lower part of the case is provided with lugs, pins, or other supports for a dial, D, which is confined by means of suitable fastenings, E.

To the lower or rear face of the dial is secured metallic frame F, which carries the working parts of the device. To said frame, at one end, is secured a bridge, G, similar to the bridge forming one of the bearings of the journal of a watch escapement-wheel.

The letter H indicates the index or pointer shaft. This shaft is journaled in a central bearing in the frame F and in a bearing in the bridge, so as to be capable of rotating freely, and projects through the dial at its center, and has an index or finger, H, secured to it, The said shaft is provided with a pinion, I, with which two toothed segments, K L, engage. The segment L is journaled on an arbor, 1?,

secured to the supporting-frame, and has a short extension, Q, provided with a series of apertures, whereby may be adjustably connected to it a small link, It. The said link connects with one end of the bimetallic strip S, which is curved, and fastened at its other end to the supporting-frame.

The regulating device consists of a cogged segment, K, substantially like the segment L, already described, and pivoted at the point 70, so that its teeth engage with the pinion I on the pointer-shaft. 1t thereby offers a certain amount of resistance to the movement of the pinion, not sufficient to stop it, but enough to neutralize the minute fluctuations on the bimetallic strip, which, when magnified by the length of the pointer, are quite appreciable.

A spring, 0, bears on a pin near the end of temperature on the dial, which is properly graduated on its face. The segment Kis actuated by the hair-sprin g to return the index (and keep it from slipping hack) to its, normal poment L, the pinion I on the pointer-shaft, and I0 sition,in addition to the force exerted upon it a governing device consisting of the pivoted for the purpose by the bimetallic strip, thus cogged segment K, engaging with said pinion,

insuring its complete return. and the spring 0,substantia1ly as and for the 5 Having thus described my invention, what purposes set forth.

I claim, and desire to secure by Letters Pat- WILLIAM A. -WALES.

ent, is- Witnesses:

In a thermometer, the combination of a bi- GEO. H. BOURNE, metallic strip adjustably connected to the seg- RUFUS FOLSOM. 

